The present invention relates generally to the field of cardiac pacing systems, and more particularly to a cardiac pacing device having pacing control for minimizing a ventricular pause that can follow the delivery of an atrial anti-tachycardia pacing (ATP) therapy.
Modern cardiac pacing devices and systems, such as implantable pacemakers and cardioverter-defibrillators, are designed for efficient dual or multiple chamber pacing, as well as for detection and treatment of dangerous cardiac arrhythmias. A dual chamber pacing device commonly provides an atrial tracking, synchronous pacing mode (such as DDD or DDDR), whereby the ventricle is paced in synchrony with sensed and/or paced atrial activity. This type of pacing scheme approximates the normal healthy coordination between the atrium and the ventricle and, thus, optimizes cardiac output of the heart.
If the atrium is seized with an arrhythmia, however, most modern pacing devices will switch from an atrial tracking, synchronous pacing mode (such as DDD) to a non-tracking, atrial-ventricular (AV) sequential pacing mode (such as DDI), in which the ventricle is paced in response to pulsed atrial activity but not sensed atrial activity. To combat the atrial arrhythmia, the pacing device commonly will select and administer an ATP therapy comprising a plurality of carefully controlled, rapidly administered pulses to the atrium. During delivery of the ATP therapy to the atrium, the pacing device will switch to a special therapy mode (such as AOO with VVI backup) in which the ventricle is paced independent of atrial activity. That is, neither paced nor sensed atrial events trigger pacing in the ventricle. During the special therapy mode, the ventricle is commonly paced at a patient-specific lower rate interval (LRI), or at a sensor rate if the patient's current activity levels justify a higher rate.
Upon delivery of the last atrial pacing pulse of the ATP therapy, the pacing device commonly reverts back to the non-tracking, AV sequential pacing mode (e.g., DDI). This transition back, however, may result in a ventricular pulse-to-ventricular pulse (V-V) interval between the last ventricular pulse delivered prior to the cessation of the ATP therapy and the first ventricular pulse (paced or intrinsic) delivered after completion of the ATP therapy that is significantly longer than the LRI.
This is especially true if the last atrial pulse of the ATP therapy occurs immediately prior to the next scheduled ventricular pulse. This long V-V interval experienced upon transition between the pacing device's therapy mode and non-tracking, AV sequential mode is referred to herein as a ventricular pause.
A ventricular pause that is greater than the LRI presents three potentially negative effects. First, the long ventricular pause may produce undesirable symptoms in some patients. Second, alternating between relatively short and long ventricular intervals could be potentially pro-arrhythmic. Third, the long ventricular pause may result in confusion for the patient's physician because data stored in the device may appear as though the patient was paced at a rate lower than the programmed LRI.